Creating Captcha for Contact Form in WordPress

A detailed guide on how to add Captcha to the contact form in WordPress to protect your website from spam and automated bots.

This article will guide you through the process of integrating Captcha into the contact form in WordPress using Google reCAPTCHA. We will go through the installation and configuration steps to ensure your site is secure.

PHP Code

To add Captcha to the contact form, you can use the following code in the functions.php file of your theme or a custom plugin:

// Add reCAPTCHA to contact form
function my_contact_form_captcha() {
    ?>
    <div class="g-recaptcha" data-sitekey="YOUR_SITE_KEY"></div>
    <?php
}
add_action('wp_footer', 'my_contact_form_captcha');

// Handle Captcha verification
function verify_captcha($fields, $form) {
    if (isset($_POST['g-recaptcha-response'])) {
        $response = $_POST['g-recaptcha-response'];
        $remoteip = $_SERVER['REMOTE_ADDR'];
        $secret = 'YOUR_SECRET_KEY';

        $url = 'https://www.google.com/recaptcha/api/siteverify';
        $data = [
            'secret' => $secret,
            'response' => $response,
            'remoteip' => $remoteip
        ];

        $options = [
            'http' => [
                'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
                'method'  => 'POST',
                'content' => http_build_query($data),
            ],
        ];
        $context  = stream_context_create($options);
        $result = file_get_contents($url, false, $context);
        $resultJson = json_decode($result);
        
        if (!$resultJson->success) {
            // Handle when Captcha is invalid
            return new WP_Error('captcha_error', 'Please verify the Captcha.');
        }
    } else {
        return new WP_Error('captcha_error', 'Please verify the Captcha.');
    }
}
add_action('contact_form_before_send', 'verify_captcha', 10, 2);

Detailed explanation:

1. my_contact_form_captcha(): This function adds the reCAPTCHA widget to the footer of the page; replace YOUR_SITE_KEY with your site key.
2. verify_captcha(): This function handles Captcha verification after the user submits the form. It sends a request to Google to validate the Captcha code and processes the response.
3. add_action('wp_footer', 'my_contact_form_captcha'): Adds reCAPTCHA to the footer section of WordPress.
4. add_action('contact_form_before_send', 'verify_captcha', 10, 2): Calls the Captcha verification function before sending the contact form.

System Requirements:

• WordPress 4.0 or higher
• JavaScript-enabled browser

How to install the libraries needed to run the PHP code above:

1. Register for an account at Google reCAPTCHA.
2. Create a site key and secret key for your domain.
3. Replace YOUR_SITE_KEY and YOUR_SECRET_KEY in the above PHP code.

Tips:

• Consider using reCAPTCHA v2 or v3 for better security.
• Double-check DNS settings if you encounter issues with Captcha verification.

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